FIX: Traceback would occur when a system_message is raised, which could be due to component with same name already existing or 'Remove selected items' pressed with no items selected. Thanks to nike-17@… for the report.

FIX: Package was missing __init__.py file, which could result in a failure of the plugin to load.

FIX: Removed rollbacks on db upgrade, which fail in Trac 1.0dev and later since the db connection is read-only.

Refs #10155: Partial support for autocompleting the reporter, owner and cc fields on the query page. The dynamic behavior has not yet been implemented, for binding autocomplete behavior to dynamically added filters.